A cabin attendant helped to steer a Heathrow-bound passenger plane to safety after the co-pilot suffered a breakdown in mid-air, investigators have revealed.

The flight attendant was promoted to the cockpit after the captain of the Air Canada service ordered his colleague to be handcuffed and dragged from his seat. The female attendant, a qualified commercial pilot, came forward after the captain asked the 155 passengers and crew if there were any professional pilots on board. The unnamed attendant sat in the co-pilot's seat of the Boeing 767-333 jet as the Toronto to Heathrow flight was diverted to Shannon airport in Ireland on January 28.

The report by the Irish Air Accident Investigation Unit said the captain noted that his first officer was "quite harried" before takeoff and later became belligerent and uncooperative, "which convinced the commander he was now dealing with a crew member who was effectively incapacitated". The unnamed officer was taken to a psychiatric unit and was flown home 11 days later.